So are you dismissing the results and findings from DxO? Or is not more about how to interprete them? Do you think DxO uses Imatest? I don't find the relevance of the example unless you think that DxO are amateurs.

The use the slanted edge method (google DxO Analyzer) to measure the MFT curves in the RAW file on each channel. Then they compute some kind of weighed average, which they call P-Mpix. They would not tell us how they computed that score, and they are hiding (now) the MTF data used to compute it.

They measure (compute actually) the MTF after the signal has been sampled. Their numbers, and those of just about everybody else, are affected by both the analog image projected on the sensor, the AA included, and by the effects of the discretization. Different targets and methods, and even different angles of the slanted edge will produce different numbers even for a lens with no astigmatism.